How to examine cells and tissues 2 Flashcards
What does the Latin word ‘tissue’ mean?
Woven
What are the broad tissue classifications?
Epithelial
Connective
Muscle
Nerve
Where are epithelial cells often found?
On the edges of other tissues and surrounding other tissues
What does it mean when epithelial cells are described as polarised? (Usually when they’re at the surfaces)
Their top and bottom parts are very different
What do epithelial cells always have?
A basement membrane on the basal (lower surface)
Basement membrane is composed of the basal lamina and, below it, the reticular lamina
The reticular lamina may not be present but the basal lamina will always be there
What are clusters of epithelial cells found deep within other tissues called?
Glands
Epithelial cells often secrete something. If they do, where do they release it from?
The apical surface or the epithelium
How are epithelial cells held together?
By strong anchoring proteins
How do epithelial cells communicate?
Through junctions at their lateral and basal surfaces, rarely through the apical surfaces
What types of connective tissue are there?
Fibrous (tendons)
Loose (under skin)
Specialised (blood, bone, cartilage, adipose etc.)
What are the main cells in connective tissue?
Fibroblasts, chondrocytes, osteocytes/blasts/clasts, stem cells, progenitor cells, bone marrow, blood, adipocytes
What is the main cell type in connective tissue?
Fibroblasts
This is immature; when it’s mature, it becomes fixed in its phenotype
Can change into chondrocytes, osteocytes etc.
What do the main cells in connective tissues do?
Lay down extracellular proteins and glycoproteins, produce gels for contact between tissues
What are the main products of connective tissues?
Fibres (mainly collagen, some elastin in foetal development and many others)
Ground substance
Wax and gel-like materials (glucosaminooglycans)
What do glucosaminoglycans do?
Attract water, act as a lubricant or as a shock absorber
What are the three connective tissue layers of a spinal nerve?
Epineurium, perineurium, endoneurium
What are the three types of muscle cell?
Skeletal
Cardiac
Smooth
Which muscle cell types are striated?
Cardiac and skeletal
Which muscle cell types are involuntarily controlled?
Cardiac and smooth
What are the functions of muscle cells?
Movement, stability, movement of tissue contents, secretion of hormones (minor function)
What hormones can muscle cells secrete?
Natriuretic factors (ANB, eg.), myostatins (stop adjacent muscle cells from growing)
Which muscle tissues types(s) are under voluntary control?
Skeletal
What are the units of length sometimes used in medicine called and what do they mean in terms of metres?
milli (m) 10^-3
micro (μ) 10^-6 (standard for a cell)
nano (n) 10^-9
pico (p) 10^-12
How large is a typical RBC?
7-8μm
Which is the only cell visible to the naked eye?
Oocyte (4,000,000μm^3)
What is the limit of resolution?
The smallest distance by which two objects can be separated and still be distinguishable as two separate objects
What are some pros and cons of using a light microscope over an electron microscope?
Light - can see colours, large field of view, cheap, easy, can view living objects, but lower magnification and resolution
By how much does the magnification and resolution improve for an electron vs light microscope?
1000x
How do you prepare a slide for a transmission electron microscope? What about for a Scanning EM?
Both - Fix with Glutaraldehyde, Embed in Epoxy resin, Stain (e.g. Osmium tetroxide)
For TEM, additionally use a microtome with diamond knives to cut the tissue
Why do we fix tissue for microscopy? When do we not need to?
To prevent putrefaction
Needs to be very thin (2-20μm) so it is transparent
Small samples of tissues
Not necessary if using cell culture or as a diagnostic frozen section
How are tissue samples prepared for light microscopy?
Preserved in formalin (formaldehyde, buffered)
Embed in melted Paraffin wax, then cooled to set
Stained (H&E)
How could an endometrial tissue sample be obtained?
Biopsy
Curettage
Pipelle
Hysterectomy
How does an aldehyde fixative fix the sample?
Methylates the proteins, thus cross-linking them, fixing them in that moment in time
What are some ways of obtaining tissue samples?
Venepuncture, bone marrow aspiration, biopsy, blood smears, cheek swabs
What are some stains used in histology, apart from H&E?
Masson’s trichrome (produce red keratin and muscle fibres, blue or green collagen and bone, light red or pink cytoplasm,
and dark brown to black cell nuclei; doesn’t identify sugars)
Periodic Acid-Schiff stain ( Identifies anything with a sugar
sugar around attached - glycocalyx)
What do Haematoxylin/Eosin do?
H - stains acids blue, eg. nucleus
E - stains proteins pink eg. cytoplasm, EM
How does confocal microscopy work?
Fluorescently labelled antibody binds to specific antigen of a protein in the cells
Laser excites the fluorescent molecules… emit light, detected, computer can turn this into a sharp 3D image
How do you prepare live cells in histology?
Cut and dice until EM breaks down \+ collagenase and DNAse as some nuclei broke, and DNA is very sticky Centrifugation to separate cell types Culture cells (view under phase contrast microscope)
What needs to be maintained constant in the internal environment of a cell culture?
Concentration of oxygen, carbon dioxide, salt and other electrolytes
Concentration of nutrients, waste products
pH of internal environment
Temperature of internal environment
Volume and pressure of fluid and cell compartments equalised
How are live cell cultures observed?
Using a phase contrast microscope
What are some advantages of using cell cultures?
Absolute control over the physical environment
All cells will be the same
Less need for animal models (ethical)
What are some disadvantages of using cell cultures?
Hard to maintain
Only grow small amount of tissue at high cost
Dedifferentiation (might turn to different cell type)
Instability, aneuploidy (could lose DNA/turn into cancer cell)
3 dimensional architecture is lost
Influence of other cells/tissues not maintained
